Inhomogeneous electroluminescence(EL)of InGaN green LEDs grown on mesh-patterned Si(111)substrate had been investigated.Sample with n-AlGaN inserted between the pre-strained layers and the first quantum well showed th...Inhomogeneous electroluminescence(EL)of InGaN green LEDs grown on mesh-patterned Si(111)substrate had been investigated.Sample with n-AlGaN inserted between the pre-strained layers and the first quantum well showed the inhomogeneous EL in the low current density range.Near-field EL emission intensity distribution images depicted that inhomogeneity in the form of premature turn-on at the periphery of the LED chip,results in stronger emission intensity at the edges.This premature turn-on effect significantly reduces the luminous efficacy and higher ideality factor value due to locally current crowding effect.Raman measurement and fluorescence microscopy results indicated that the partially relaxed in-plane stress at the edge of the window region acts as a parasitic diode with a smaller energy band gap,which is a source of edge emission.Numerical simulations showd that the tilted triangular n-AlGaN functions like a forward-biased Schottky diode,which not only impedes carrier transport,but also contributes a certain ideality factor.展开更多
GaN-based blue light emitting diodes （LEDs） have undergone great development in recent years, but the improvement of green LEDs is still in progress. Currently, the external quantum efficiency （EQE） of GaN-based g...GaN-based blue light emitting diodes （LEDs） have undergone great development in recent years, but the improvement of green LEDs is still in progress. Currently, the external quantum efficiency （EQE） of GaN-based green LEDs is typically 30%, which is much lower than that of top-level blue LEDs. The current challenge with regard to GaN-based green LEDs is to grow a high quality InGaN quantu.m well （QW） with low strain. Many techniques of improving efficiency are discussed, such as inserting A1GaN between the QW and the barrier, employing prestrained layers beneath the QW and growing semipolar QW. The recent progress of GaN-based green LEDs on Si substrate is also reported： high efficiency, high power green LEDs on Si substrate with 45.2% IQE at 35 A/cm2, and the relevant techniques are detailed.展开更多
GaN based MQW epitaxial layers were grown on Si （111） substrate by MOCVD using AIN as the buffer layer. High light extraction LEDs were prepared by substrate transferring technology in combination with thin-film and...GaN based MQW epitaxial layers were grown on Si （111） substrate by MOCVD using AIN as the buffer layer. High light extraction LEDs were prepared by substrate transferring technology in combination with thin-film and flip-chip design. The blue and white 1.1 × 1.1 mm2 LED lamps are measured. The optical powers and external quantum efficiency for silicone encapsulated blue lamp are 546 mW, and 50.3% at forward current of 350 mA, while the photometric light output for a white lamp packaged with standard YAG phosphor is 120.1 lm.展开更多
由于硅具有价格低、热导率高、大直径单晶生长技术成熟等优势以及在光电集成方面的应用潜力,GaN/Si 基器件成为一个研究热点。然而,GaN 与 Si 之间的热失配容易引起薄膜开裂,这是限制 LED 及其它电子器件结构生长的一个关键问题。近年来...由于硅具有价格低、热导率高、大直径单晶生长技术成熟等优势以及在光电集成方面的应用潜力,GaN/Si 基器件成为一个研究热点。然而,GaN 与 Si 之间的热失配容易引起薄膜开裂,这是限制 LED 及其它电子器件结构生长的一个关键问题。近年来,随着工艺的发展,GaN 晶体质量得到大幅度的提高。同时不少研究小组成功地在Si 衬底上制造出 LED。介绍了 GaN 薄膜开裂问题及近期硅衬底 GaN 基 LED 的研究进展。展开更多
基金the National Key Research and Development Program of China(Grant Nos.2017YFB0403105 and 2017YFB0403100)the National Natural Science Foundation of China(Grant Nos.11674147,61604066,51602141,and 11604137).
文摘Inhomogeneous electroluminescence(EL)of InGaN green LEDs grown on mesh-patterned Si(111)substrate had been investigated.Sample with n-AlGaN inserted between the pre-strained layers and the first quantum well showed the inhomogeneous EL in the low current density range.Near-field EL emission intensity distribution images depicted that inhomogeneity in the form of premature turn-on at the periphery of the LED chip,results in stronger emission intensity at the edges.This premature turn-on effect significantly reduces the luminous efficacy and higher ideality factor value due to locally current crowding effect.Raman measurement and fluorescence microscopy results indicated that the partially relaxed in-plane stress at the edge of the window region acts as a parasitic diode with a smaller energy band gap,which is a source of edge emission.Numerical simulations showd that the tilted triangular n-AlGaN functions like a forward-biased Schottky diode,which not only impedes carrier transport,but also contributes a certain ideality factor.
基金Project supported by the Key Program of the National Natural Science Foundation of China(Grant No.61334001)the National Natural Science Foundation of China(Grant Nos.11364034 and 21405076)+1 种基金the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(Grant No.2011BAE32B01)the National High Technology Research and Development Program of China(Grant No.2011AA03A101)
文摘GaN-based blue light emitting diodes （LEDs） have undergone great development in recent years, but the improvement of green LEDs is still in progress. Currently, the external quantum efficiency （EQE） of GaN-based green LEDs is typically 30%, which is much lower than that of top-level blue LEDs. The current challenge with regard to GaN-based green LEDs is to grow a high quality InGaN quantu.m well （QW） with low strain. Many techniques of improving efficiency are discussed, such as inserting A1GaN between the QW and the barrier, employing prestrained layers beneath the QW and growing semipolar QW. The recent progress of GaN-based green LEDs on Si substrate is also reported： high efficiency, high power green LEDs on Si substrate with 45.2% IQE at 35 A/cm2, and the relevant techniques are detailed.
文摘GaN based MQW epitaxial layers were grown on Si （111） substrate by MOCVD using AIN as the buffer layer. High light extraction LEDs were prepared by substrate transferring technology in combination with thin-film and flip-chip design. The blue and white 1.1 × 1.1 mm2 LED lamps are measured. The optical powers and external quantum efficiency for silicone encapsulated blue lamp are 546 mW, and 50.3% at forward current of 350 mA, while the photometric light output for a white lamp packaged with standard YAG phosphor is 120.1 lm.
文摘由于硅具有价格低、热导率高、大直径单晶生长技术成熟等优势以及在光电集成方面的应用潜力,GaN/Si 基器件成为一个研究热点。然而,GaN 与 Si 之间的热失配容易引起薄膜开裂,这是限制 LED 及其它电子器件结构生长的一个关键问题。近年来,随着工艺的发展,GaN 晶体质量得到大幅度的提高。同时不少研究小组成功地在Si 衬底上制造出 LED。介绍了 GaN 薄膜开裂问题及近期硅衬底 GaN 基 LED 的研究进展。
